Study of equilibrium, kinetic and thermodynamic parameters about methylene blue adsorption onto natural zeolite
Introduction
Adsorption has been an effective separation process for a wide variety of applications, especially for removal of non-biodegradable pollutants (including dyes) from wastewater [1], [2]. Adsorption capacity and characteristic of adsorbents were always examined using adsorption isotherm [3]. The linear least-squares method to the linearly transformed adsorptive equations was widely applied to confirm the experimental data and models using coefficient of determination [3], [4], [5]. However, depending on the way adsorptive equation linearized, the error distribution changes worse [6], [7], [8], [9]. So it will be an inappropriate technique to use the linearization method for estimating the adsorptive model parameters.
Adsorption isotherms of Langmuir, Freundlich, Redlich–Peterson, Koble–Corrigan and Temkin equations and pseudo-second-order model are often adopted to predict the adsorptive process in batch mode. Although linear least-square regressive analysis is often used to calculate the relative parameters [10], [11], [12], nonlinear regressive analysis is also adopted to obtain the parameters [13], [14], [15], [16]. The comparison of linear and nonlinear regressive method about these models had been analyzed [5], [6], [8].
Natural zeolite is easily obtained in many places and has been used as an adsorbent to remove dyes, ammonia ions and heavy metals [17], [18], [19]. Methylene blue (MB) is selected as a model compound in order to evaluate the capacity of natural zeolite for the removal of MB from its aqueous solutions in batch mode.
Thus, in the present study, linear and nonlinear method was used to estimate the isotherms parameters, kinetic model parameters. A comparative analysis was made between the linear and nonlinear method in estimating the relative parameters for the adsorption of MB onto zeolite. The error of prediction from two methods was analyzed.
The Langmuir adsorption isotherm has been successfully applied to many pollutants adsorption processes and has been the most widely used sorption isotherm for the sorption of a solute from a liquid solution [20]. The saturated monolayer isotherm can be represented asThe above equation can be rearranged to the common linear form:where ce is the equilibrium concentration (mg l−1); qe is the amount of MB adsorbed onto per unit mass of zeolite (mg g−1); qm is qe for a complete monolayer (mg g−1), a constant related to sorption capacity; and KL is a constant related to the affinity of the binding sites and energy of adsorption (l mg−1).
Freundlich isotherm is an empirical equation describing adsorption onto a heterogeneous surface. The Freundlich isotherm is commonly presented as [21]:where KF and n are the Freundlich constants related to the adsorption capacity and adsorption intensity of the sorbent, respectively. Eq. (3) can be linearized by taking logarithms:
The three-parameter Redlich–Peterson equation which has a linear dependence on concentration in the numerator and an exponential function in the denominator has been proposed to improve the fit by the Langmuir or Freundlich equation and is given by Eq. (5) [22]:where A, B and g are the Redlich–Peterson parameters, g lies between 0 and 1. For g = 1, Eq. (5) converts to the Langmuir form.
Three isotherm constants, A, B and g can be evaluated from the linear plot represented by Eq. (6) using a trial and error optimization method:
Koble–Corrigan model is also three-parameter equation for the representing equilibrium adsorption data. It is a combination of the Langmuir and Freundlich isotherm type models and is given by Eq. (7) [23]:where A, B and n are the Koble–Corrigan parameters.
Three isotherm constants, A, B and n can also be evaluated from the linear plot represented by Eq. (8) using a trial and error optimization method:
The derivation of the Temkin isotherm assumes that the fall in the heat of adsorption is linear rather than logarithmic, as implied in the Freundlich equation. The Temkin isotherm [24]:where A and B are isotherm constants.
The pseudo-second-order equation based on adsorption equilibrium capacity can be expressed as [8], [25]:where k2 is the rate constant of pseudo-second-order adsorption (g mg−1 min−1).
Integrating this equation for boundary conditions for t = 0, q = 0 gives
The linear pseudo-second-order equation can be expressed as
The equilibrium sorption capacity, qe, and the pseudo-second-order rate constant, k2, can be determined using linear regressive analysis by Eq. (12) or nonlinear regressive analysis by Eq. (11), respectively.
In order to confirm the fit model for the adsorption system, it is necessary to analyze the data using error analysis, combined the values of determined coefficient (R2) from regressive analysis. The calculated expressions of some error functions are as follows [9], [26], [27]:
- (1)
The sum of the squares of the errors (SSE):
- (2)
The sum of the absolute errors (SAE):
- (3)
The average relative error (ARE):
- (4)
The average relative standard error (ARS):where n is the number of experimental data points, qc is the predicted (calculated) quantity of MB adsorbed onto zeolite according to the isotherm equations and qe is the experimental data.
Section snippets
Materials
The dye used in batch experiments was methylene blue (C.I. no. 52015). MB has a molecular weight of 373.9 g mol−1, which corresponds to methylene blue hydrochloride with three groups of water. The stock solutions of MB were prepared in distilled water (1 g l−1). All working solutions were prepared by diluting the stock solution with distilled water to the desired concentration. The values of solution pH were near 7.5.
The natural zeolite used in the present study was obtained from Xinyang city in
The effect of pH
Fig. 1 shows the effect of solution pH on MB adsorption onto zeolite at various initial solution pH for an initial dye concentration of 30 mg l−1 and zeolite dose of 6 g l−1.
From Fig. 1, the solution pH affected the values of qe. When the value of pH was from 4 to 10, the adsorption quantity was approximately constant. As the initial pH of MB solution is near 7.5, the pH of experimental solution was not adjusted.
The effect of salt concentration on adsorption
Fig. 2 shows the effect of various concentration of NaCl and CaCl2 solution on the
Conclusion
Present study showed that all the five isotherms, Langmuir, Freundlich, Redlich–Peterson, Koble–Corrigan and Temkin equation, could represent the equilibrium adsorption of MB onto natural zeolite. The kinetic process can be predicted by pseudo-second-order model. Both linear method and nonlinear method were suitable to predict the adsorption process. The Redlich–Peterson equation was best fitted to the equilibrium data from two methods. Nonlinear method was better than linear method about
Acknowledgements
The authors express their sincere gratitude to the Henan Science and Technology Department in China, for the financial support of this study. The authors also express thanks to China Postdoctoral Science Foundation (No. 20070420811) for financial support.
References (34)
Non-conventional low-cost adsorbents for dye removal: a review
Bioresour. Technol.
(2006)- et al.
Remediation of dyes in textile effluent: a critical review on current treatment technologies with a proposed alternative
Bioresour. Technol.
(2001) Application of biosorption for the removal of organic pollutants: a review
Process Biochem.
(2005)- et al.
Equilibrium biosorption isotherm for lead ion on chaff
J. Hazard. Mater.
(2005) - et al.
Equilibrium uptake and sorption dynamics for the removal of a basic dye (basic red) using low cost adsorbents
J. Colloid Interface Sci.
(2003) - et al.
Regression analysis for the sorption isotherms of basic dyes on sugarcane dust
Bioresour. Technol.
(2005) Comparative analysis of linear and non-linear method of estimating the sorption isotherm parameters for malachite green onto activated carbon
J. Hazard. Mater.
(2006)Second-order kinetic model for the sorption of cadmium onto tree fern: a comparison of linear and non-linear methods
Water Res.
(2006)- et al.
Comparison of linear and nonlinear analysis in estimating the Thomas model parameters for methylene blue adsorption onto natural zeolite in fixed-bed column
J. Hazard. Mater.
(2007) - et al.
Removal of lead(II) by adsorption using treated granular activated carbon: batch and column studies
J. Hazard. Mater.
(2005)
Removal of reactofix golden yellow 3 RFN from aqueous solution using wheat husk—an agricultural waste
J. Hazard. Mater.
Copper(II) and lead(II) removal from aqueous solution in fixed-bed columns by manganese oxide coated zeolite
J. Hazard. Mater.
The biosorption of Acid Red 337 and Acid Blue 324 on Enteromorpha prolifera: the application of nonlinear regression analysis to dye biosorption
Chem. Eng. J.
Heavy metal removal in a biosorption column by immobilized M. rouxii biomass
Bioresour. Technol.
Biosorption of methylene blue from aqueous solution by fallen phoenix tree's leaves
J. Hazard. Mater.
Removal of methylene blue from aqueous solution by chaff in batch mode
J. Hazard. Mater.
Characterisation and environmental application of an Australian natural zeolite for basic dye removal from aqueous solution
J. Hazard. Mater.
Cited by (435)
Reusing spent fluid catalytic cracking catalyst as an adsorbent in wastewater treatment applications
2023, Materials Today SustainabilityUsing zeolite filters to reduce activated carbon use in micropollutant removal from wastewater
2023, Journal of Water Process EngineeringCharacterization of physicochemical properties of activated carbons prepared from penicillin mycelial residues and its adsorption properties for VOCs
2023, Journal of Environmental Chemical Engineering